This invention relates to a tire building apparatus capable of forming tires of various tires.
Hitherto used tire building apparatuses have been known, for example, as disclosed in Japanese Patent Application Publication No. 47-21,836. This disclosed tire building apparatus comprises a forming drum to which tire constituting members are attached. Annular bead rings are movable in axial directions of the forming drum for driving beads grasped on their inner circumferences into predetermined positions in the tire constituting members. Annular turning-up holders are movable in the axial directions of the forming drum for turning up parts of the tire constituting members on axially outer sides of the bead driving positions about the beads with the aid of bladders. Each of the annular bead rings is separable into a plurality of arcuate segments circumferentially separated and radially movable upon rocking. On the other hand, the annular turning-up holders are circumferentially continuous. In forming a tire by means of such a tire building apparatus, after a tire constituting member has been attached to the tire forming drum, the bead rings grasping beads on their inner circumferences are moved axially inwardly to drive the beads into predetermined positions in the tire constituting member. Thereafter, the bead rings are moved axially outwardly so as to expand the turning-up holders to retract the bead rings radially outwardly. Then, while the bladders are being expanded, the turning-up holders are moved axially inwardly so that parts of the tire constituting member on axially outer sides of the bead driven positions are turned up about the beads by means of the bladders.
With such a tire building apparatus of the prior art, the turning-up holders are circumferentially continuously annular and the bead rings are circumferentially divided into a plurality of parts and radially movable in order to avoid any interference of the bead rings with the bladders. Therefore, the tire building apparatus constructed as above described can form only tires of one size. In order to form tires of different sizes, the bead rings and the turning-up holders must be exchanged with others to meet sizes of the tires every time when the size is changed. Therefore, troublesome and time-consuming operations for the exchange of the members of the apparatus are required, which considerably lower the efficiency in the production line. Moreover, various kinds of bead rings and turning-up holders are needed, which unavoidably increase cost for manufacturing the apparatus. Further, as diameters of bead rings are previously fixed at certain values, irregularities in diameter of the bead rings directly result in inferior quality of tires produced such as an inconsistency of centers of the beads and bead rings.